Integrated circuit inputs and outputs are provided through controlled collapse chip connections (C4s). As integrated circuits become smaller, increasing the number of C4s that can be placed on the integrated circuits is becoming a challenge. The challenge arises because the number of inputs and outputs (port density) desired for integrated circuits is increasing, but wafer surface area that is available for forming the inputs and outputs is decreasing. Increasing port density for integrated circuits can increase the functionality provided by the integrated circuits.
One way to increase port density and provide additional high speed capable inputs and outputs for an integrated circuit is by forming light detecting diodes (i.e., photo-diodes) and light emitting diodes on a wafer. Traditionally, light detecting diodes and light emitting diodes, both also referred to as optical ports, are formed on a front-side of the wafer. In addition, back-end-of-line (BEOL) processing is performed to create BEOL metal wiring and dielectric levels, and C4 pads on the front-side of the wafer. The BEOL metal wiring and dielectric levels, and C4 pads integrate the light detecting diodes and the light emitting diodes with other circuitry (i.e., other semiconductor devices) on the front-side of the wafer. Although a semiconductor structure having light detecting diodes and light emitting diodes on the front-side of the wafer may provide a performance benefit over C4 pads, generally such a semiconductor structure does not completely address the challenge of how to increase port density as technological advancements continue to result in a decrease of available wafer surface area.
Moreover, BEOL processing requires the BEOL metal wiring and dielectric levels to be formed on top of the light detecting diodes, light emitting diodes, and other semiconductor devices that may be formed on the front-side of the wafer. The BEOL dielectric isolates the BEOL metal wiring from certain areas of the wafer. However, the BEOL dielectric can cause a decrease in performance of the semiconductor devices formed on the wafer. Specifically, the BEOL dielectric can cause attenuation of light signals being emitted or detected by the diodes, and the more the BEOL metal wiring the greater the attenuation of the light signals. The attenuation of the light signals described above can decrease the performance of light detecting and light emitting diodes. Accordingly, the challenge of forming a semiconductor structure having a light detecting diode and a light emitting diode that increases port density for an integrated circuit, and reduces attenuation of light signals being emitted and detected by the diodes respectively, continues to persist. Reducing the attenuation can enhance the performance of the diodes and consequently integrated circuits that utilize the diodes.